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Journal of the Air & Waste Management Association

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Concept of sustainable waste management in thecity of Zagreb: Towards the implementation ofcircular economy approach

Bojan Ribić, Neven Voća & Branka Ilakovac

To cite this article: Bojan Ribić, Neven Voća & Branka Ilakovac (2017) Concept of sustainablewaste management in the city of Zagreb: Towards the implementation of circular economyapproach, Journal of the Air & Waste Management Association, 67:2, 241-259, DOI:10.1080/10962247.2016.1229700

To link to this article: http://dx.doi.org/10.1080/10962247.2016.1229700

Accepted author version posted online: 20Sep 2016.Published online: 20 Sep 2016.

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TECHNICAL PAPER

Concept of sustainable waste management in the city of Zagreb: Towards theimplementation of circular economy approachBojan Ribića, Neven Voćab, and Branka Ilakovacc

aZagreb City Holding, Zagreb, Croatia; bFaculty of Agriculture, University of Zagreb, Zagreb, Croatia; cCroatian Agency for Environment andNature, Zagreb, Croatia

ABSTRACTImprovement of the current waste management is one of the main challenges for most munici-palities in Croatia, mainly due to legal obligations set in different European Union (EU) directivesregarding waste management, such as reduction of waste generation and landfilling, or increaseof separately collected waste and recycling rates. This paper highlights the current waste manage-ment in the city of Zagreb by analyzing the waste generation, collection, and disposal scenarioalong with the regulatory and institutional framework. Since the present waste managementsystem mainly depends upon landfilling, with the rate of separate waste collection and recyclingfar from being adequate, it is necessary to introduce a new system that will take into account thecurrent situation in the city as well as the obligations imposed by the EU. Namely, in the comingyears, the Waste Framework and Landfill Directives of the European Union will be a significantdriver of change in waste management practices and governance of the city of Zagreb. Atpresent, the yearly separate waste collection makes somewhat less than 5 kg per capita of variouswaste fractions, i.e., far below the average value for the (28) capital cities of the EU, which is 108kg per capita. This is possible to achieve only by better and sustainable planning of futureactivities and facilities, taking into account of environmental, economic, and social aspects ofwaste management. This means that the city of Zagreb not only will have to invest in newinfrastructure to meet the targets, but also will have to enhance public awareness in diverting thiswaste at the household level. The solution for the new waste management proposed in this paperwill certainly be a way of implementing circular economy approach to current waste managementpractice in the city of Zagreb.

Implications: Municipal waste management in the developing countries in the EU (new easternEU members) is often characterized by its limited utilization of recycling activities, inadequatemanagement of nonindustrial hazardous waste, and inadequate landfill disposal. Many cities inEastern Europe and Zagreb as well are facing serious problems in managing municipal wastes dueto the existing solid waste management system that is found to be highly inefficient. Theproposed scenario for city of Zagreb in the paper is an innovative upgrading of municipalwaste management based on the waste management hierarchy and circular economy approach.

PAPER HISTORYReceived April 26, 2016Revised August 2, 2016Accepted August 12, 2016

Introduction

Waste is a pressing environmental, social, and economicissue, and one of the biggest challenges faced by everyurban area in the world. Although the quantity andquality of solid waste generated by urban areas in thedeveloping countries are low compared with Westerndeveloped and industrialized countries, the municipalsolid waste management still remains inadequate (Ilicand Nikolic, 2016). Waste management has been widelyrecognized as a technical problem that is strongly influ-enced by various political, legal, sociocultural, environ-mental, and economic factors and by resources availableto tackle it. Moreover, the interrelationships of thesefactors are usually very complex when it comes to the

waste management. Appropriate solutions for the com-plex waste management problems should be analyzedfrom the system perspective, taking into account all ofthe above factors that are present in a local area(Mashayekhi, 1993; Vesilind et al., 2002; Kum et al.,2005). Failure to do so may lead to ill-designed solutionsthat may not be effective enough to give any productiveresults in waste management. This also refers to the caseof municipal waste management in the city of Zagreb,which currently relies only upon landfilling, with a lowpercentage of recycling rates.

Increase of the generated waste amounts is mostlydue to population growth, lifestyle changes, develop-ment, and consumption of products with materials that

CONTACT Neven Voća nvoca@agr.hr Faculty of Agriculture, University of Zagreb, Svetosimunska cesta 25, Zagreb, Croatia.

JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION2017, VOL. 67, NO. 2, 241–259http://dx.doi.org/10.1080/10962247.2016.1229700

© 2017 A&WMA

are more or less biodegradable, which created diversechallenges for municipal solid waste management invarious cities of the world. Review of the literatureespecially reveals the differences between municipalwaste management in developed and developing coun-tries. In the most developed countries, public health isno longer a major driver for the improvement of thewaste management. The focus is primarily on optimi-zation of waste management practices, with a broadergoal of resource conservation (McDougall and Hruska,2000; Collivignarelli et al., 2004; Wilson, 2007). Inrecent years, there has been a tendency towards reduc-tion of the total production of municipal waste. Thistrend is caused both by the international economiccrisis that brought out decreasing consumption andby new models of production and consumption thatare more conscientious about limiting the productionof waste (Paolo and Paola, 2015).

The benefits of successful upgrading of municipalwaste management in the waste management hierarchyare not only limited to a more efficient use of resourcesand a reduced waste burden on the natural environment.Even though greenhouse gas (GHG) emissions frompostconsumer waste and wastewater are a small contri-butor (about 3%) to total global anthropogenic GHGemissions, efficient waste management will definitelyhave impact on GHG emission reduction. Methaneemissions from landfilled municipal waste have declinedconsiderably in the past decade, whereas the benefitsfrom higher recycling rates have grown even more.These benefits in GHG emissions derive from the factthat recycled materials replace virgin materials, thusreducing the GHG emissions from their primary pro-duction. Focus of sustainable waste management in theperiod 2001–2010 is clear evidence of reducing of GHGas a result of implemented sustainability criteria and anupward shift in the waste management hierarchy(Bogner et al., 2008; European Environment Agency[EEA], 2013; Karagiannidis et al., 2013). Sustainabledevelopment requires viable answers following eco-nomic, social, and environmental criteria. Therefore,sustainable waste management has a central role in sus-tainable development (Cucchiella et al., 2014).

Looking at the European Union (EU) only, dataindicate that landfilling of municipal waste decreasedby almost 40 million tonnes, whereas incinerationincreased by 15 million tonnes and recycling grew by29 million tonnes. However, such data aggregationfrom 32 European countries masks large differences inwaste management performance of individual coun-tries. Municipal waste management in developingcountries in the EU (new eastern EU members) isoften characterized by its limited utilization of recycling

activities, inadequate management of nonindustrialhazardous waste, and inadequate landfill disposal(EEA, 2013; Guerrero et al., 2013).

EU waste management policies aim to reduce theenvironmental and health impacts of waste andimprove Europe’s resource efficiency. The WasteManagement Strategy of the Republic of Croatia forthe period 2007–2015 establishes the framework forwaste reduction and sustainable waste management.This is a major waste management planning documentintroducing the concept of waste management hierar-chy that gives priority to waste prevention, recycling,reuse, and other types of recovery.

Reducing municipal waste can result in a wide range ofenvironmental, economic, and social benefits, such asreducing pollution in water and soil, greenhouse gas emis-sions, and loss of valuable materials (Tchobanoglous et al.,1993; Wilson, 2007; Asase et al., 2009). In addition to datagathering and processing, the researches focused on devel-opment of the waste management models and their opti-mization, which were presented in detail by Beigl et al.(2008). The published works that deal with forecasting anddevelopment of the models of municipal waste manage-ment do not rely on parameters directly related to the wastegeneration activities as such, but mainly on demographic-economic developments or possible improvements in con-nection to planning of waste transport lines (Vesling et al.,2002; Collivegnarelli et al., 2004; Bogner et al., 2008; AlaviMoghadam et al., 2009).

In the process of monitoring the municipal wastegeneration, a large number of data are collected andstored (waste types and amounts, generation flows,ways and frequency of collection, number of wasteproducers, types of waste treatment, etc.). It is, there-fore, essential to preprocess all gathered data in orderto be able to analyze them in an adequate way. Inassessing the generation of municipal waste, it shouldbe taken into account that in addition to activitiesconnected to waste management as such, social andeconomic impacts (demographic and economic devel-opments, etc.) are also crucial because they criticallydetermine the quantities of municipal waste, whichwere studied in detail by Lebersoger and Biegl (2011).

Several studies (Matos et al., 2016; Cucchiella et al.,2014; Curtis et al., 2011; Bortoleto et al., 2012, 2007;Magrinho et al., 2006;) so far have stressed that one ofthe most important factors of future plans in the wastemanagement sector is an estimate of the quantities ofmunicipal waste generation, which should be as accu-rate as possible. Further, taking into account the pre-sent trends and quantities of municipal waste, this alsoincludes separately collected waste and various socialtrends and developments (Lebersoger and Biegl, 2011).

242 B. RIBIĆ ET AL.

In addition to data that are related to waste manage-ment process as such, various sociological and eco-nomic impacts must be taken into account (numberof households, economic trends, etc.), because these areparameters that significantly influence the process ofwaste generation. This approach should provide a toolthat will enable better estimates of municipal wastegeneration, which so far has evidently been lacking,given the fact that some of the facilities for waste treat-ment in Croatia seem to be largely oversized.

The aim of this paper is present the current situationand to provide an overview of the different elements ofmunicipal waste management in the city of Zagreb, aswell as to propose a concrete solution for the imple-mentation of the sustainable waste management con-cept that is in line with current EU and nationallegislation.

The existing municipal waste management system isdescribed in terms of strategic planning and govern-ment laws and regulations; waste generation and com-position; and current treatment and disposal. Thedescription of the proposed sustainable waste manage-ment provides several recommendations for overallsystem improvement.

The novelty of the proposed approach is visible in asense that the waste management concept is movingtowards the sustainability (recycling, anaerobic diges-tion of biowaste, mechanical separation, etc.), whereonly the fraction that cannot be used will be utilizedas energy (incineration) or landfilled. This is a signifi-cant improvement compared with current practice.

This paper may be instrumental for the authoritiesand researchers of the developing and Eastern Europecountries to work towards improving their presentmunicipal solid waste management system and intro-ducing more sustainable practice according to the prin-ciples of circular economy.

Baseline conditions

According to data published by Eurostat, the statisticaldepartment of the EU, and Croatian Agency forEnvironment and Nature (CAEN), coverage of popula-tion and municipalities by organized municipal wastecollection increased from 86% in 2004 to 99% in 2014,which fulfilled the quantitative target for 2015 (90%) setby the Waste Management Strategy of the Republic ofCroatia. The generation of municipal solid waste inCroatia has increased from 979,000 tonnes in 1995 to1,637,371 tonnes in 2014. The level of municipal solidwaste peaked in 2008 with 1,788,000 tonnes (Eurostat,2010; CAEN, 2016).

Eurostat statistics for 2013 show that landfilling ratesin Croatia are very high (85%) and recycling rates arestill too low (16%) to comply with the waste hierarchyand with the 50% set in the EU Waste FrameworkDirective, which has to be met by 2020. In 2013, theamount of landfilled biodegradable municipal wastewas 115% compared with the reference year 1997.Therefore, the 2013 target (to landfill a maximumamount of biodegradable municipal waste equivalentto 75%) was clearly missed (European Commission[EC], 2015).

Total recycling significant increased between 2007and 2014, from 3.1% in 2007 to 16.5% in 2014, but isstill much below total recycling in the 28 member statesof the EU (EU28; 43.4% in 2014). The largest share intotal recycling is material recycling (14.4% in 2014),whereas composting and digestion are negligible, 2%in 2014 compared with 15.8% in EU28.

Presently Croatia is finalizing some of the major docu-ments such as new National Environmental Action Planand new Waste Management Plan (2016–2022).

The act on waste, namely, the Act on SustainableWaste Management, prescribes that waste whose valu-able properties can be used must be collected andstored separately, so as to allow the management ofsuch waste in accordance with the waste hierarchy.Producer responsibility schemes have been introducedfor six waste streams, among others for waste electricand electronic equipment (WEEE) and end-of-life vehi-cles, which are important sources of secondary materi-als. Further, the draft Waste Prevention Programme, tobe part of a new Waste Management Plan, foreseesseveral waste categories that should be considered aspriority streams. One of them is construction anddemolition waste, which has great potential from aresource efficiency perspective.

The Sustainable Waste Management Act prescribesrestrictions on disposal of biodegradable municipalwaste, including food waste. The act sets the obligationof separate collection of biowaste for composting,digestion, or energy recovery. It defines the order ofpriority of waste management, with a primary emphasison the prevention of waste generation. Among biode-gradable waste types, food waste has been defined as apriority waste stream in the draft Waste PreventionProgramme to be adopted as part of National WasteManagement Plan.

Towards sustainable waste management, Croatia iscurrently upgrading municipal solid waste managementby building regional waste management centers usingmechanical and biological waste processing technolo-gies. Many cities in Croatia are facing serious problemsin managing municipal waste due to the existing solid

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waste management system that is found to be highlyinefficient. Becoming a member of EU, it was necessaryin Croatia to make some changes in the legal frameworkin order to be in accordance with the Waste FrameworkDirective. The aim is to reduce landfilling to only resi-dual waste, and for dealing with generated waste in anenvironmentally and economically sustainable way,landfilling must be replaced by other, more sustainable,efficient, and modern processes. In addition, Croatiawould need to make an exceptional effort in order tofulfill the 50% target of the Waste Framework Directiveby 2020 as well as the diversion targets of the EU LandfillDirective. The increase in biodegradable municipalwaste since 1997—the reference year for the diversiontargets of the Landfill Directive for Croatia—makes itvery difficult for Croatia to meet the biodegradablemunicipal waste targets (EEA, 2013). Croatia might ful-fill the criteria stated in Article 11 of the EU WasteFramework Directive in order to get a derogation periodfor fulfilling the 2020 target of 50% recycling of munici-pal solid waste, as the recycling of municipal waste in2010 was 4%. A fulfillment of the 50% recycling target by2020 would require extraordinary efforts for Croatia andrequire an exceptional effort from the Croatian govern-ment, the local authorities, and a good cooperationbetween the public and private sectors in order to securesufficient treatment capacity (EEA, 2013). However,there are several Croatian municipalities with advancedwaste management system. In February 2016, the city ofPrelog and six surrounding municipalities signed theEuropean “Zero Waste 2020” strategy. In signing thestrategy, the local authorities—which are already leadersin sustainable waste management in Croatia—have com-mitted to meet the ambitious goal of 70% separatelycollected waste by 2020 (CEAN, 2016).

Background to waste policies in the EU andCroatia

According to the 7th Environment Action Programme(EC, 2013), the objectives the European Commissionwishes to achieve are general reduction of waste gen-eration per capita; waste recycling and reuse at highestrate feasible; gradual phasing out landfilling practices;and limited incineration of nonrecyclable waste. Theseproposals define ambitious plans to increase recyclingof municipal waste, phase out landfilling by 2025 of anyrecyclable materials, reduce food waste generation,extend producers’ responsibility, simplify the reportingobligations, and trim down the obligations that affectsmall and medium enterprises. Accepting the circulareconomy would help to, as in any natural cycle, reducethe amount of landfilled waste to a minimum and

would be instrumental in creating new “green jobs”(EC, 2011a, 2011b, 2015; EEA, 2016b). Key elementsof the revised waste proposal include (EC, 2015)

● EU target for recycling 65% of municipal waste by2030

● EU target for recycling 75% of packaging waste by2030

● A binding landfill target to reduce landfill to max-imum of 10% of all waste by 2030

● A ban on landfilling of separately collected waste

For this reason, the EU today regards the waste sector notonly as an important environmental issue but also as amajor opportunity for green jobs in the EU (potential ofmore than 580,000 green jobs). Besides generating thenew jobs, sustainable waste management (reusing, recy-cling, and composting) contributes to increasing thesecurity of material supplies, the competitiveness of theEuropean industries, and resource efficiency, cuttinggreenhouse gas emissions, and supporting the researchand development goals of the EU (EC, 2011a).

In order to reach the goals set in the new WastePackage, the European Commission has prepared anactivity agenda with the steps necessary to move for-ward, such as stimulate the secondary materials marketand demand for recycled materials through economicincentives and developing end-of-waste criteria, intro-duction of minimum recycled material rates, durabilityand reusability criteria, etc.

The EU legislation concerning environmental pro-tection—specially Directive 2006/66/EC (EC, 2006)addresses batteries, Directive 2008/98/EC (EC, 2008)addresses nonhazardous construction and demolitionwaste, as well as waste paper, plastics, glass, and metalfrom households, Directive 2000/53/EC (EC, 2000)addresses end-of-life vehicles, Directive 2012/19/EU(EC, 2012) addresses waste electrical and electronicequipment, and Directive 2004/12/EC (EC, 2004)addresses packaging waste, which has already beenimplemented in the national laws of the Republic ofCroatia—aims at introduction of an integral and sus-tainable waste management system, but the develop-ment of secondary raw materials market in theRepublic of Croatia and the city of Zagreb is still atits beginnings. One of the main reasons for this isgenerally undeveloped system of waste separation andlack of waste treatment (recycling) facilities.

The concept of a circular economy has recentlygained traction in European policymaking as a positive,solutions-based perspective for achieving economicdevelopment within increasing environmental

244 B. RIBIĆ ET AL.

constraints. Moreover, European countries increasinglyindicate the circular economy as a political priority.

In December 2015, the European Commission pub-lished “Closing the loop—An EU action plan for thecircular economy,” a new strategy that aims to supportthe transition to a circular economy in the EU. Theaction plan sets out a large number of initiatives thataddress all stages of the life cycle, combined with con-crete targets on waste and the development of a mon-itoring framework in cooperation with the EEA. In thisway, it takes important steps towards a circular econ-omy in Europe.

One of the established policies that support themove towards a circular economy is the EU’s five-stepwaste hierarchy established in the 2008 EU WasteFramework Directive, prioritizing the prevention ofwaste generation. The directive required EU memberstates to adopt waste prevention programs byDecember 2013, and many countries included measuresto foster innovative business models, repair, reuse, andecodesign in their programs. Policy measures aiming toreduce waste also decrease the overall need for rawmaterials and avoid both waste and the emissions cre-ated along the value chains of materials and products.They also offer a variety of opportunities to reducecosts, from the purchase of raw materials to the treat-ment and disposal of wastes (EEA, 2016a).

One of the central pillars of a circular economy isfeeding materials back into the economy and avoidingwaste being sent to landfill or incinerated, therebycapturing the value of the materials as far as possibleand reducing losses.

Framework and responsibilities in solid wastemanagement

Setting the key objectives as defined, the EU legislationis a necessary foundation of the sustainable waste man-agement in Croatia, as transposed in the Act onSustainable Waste Management (Official Gazette, 2013[94/13]). Some of its crucial elements are need toreduce waste landfilling in order to prevent its dama-ging influence on the environment as well as the neces-sity to increase use of useful waste by energy ormaterial recovery. Development of procedures andinstallations that meet these goals will result in signifi-cant reduction of landfilling of all those waste compo-nents that have negative impact on the environment,optimal degree of recycling of useful materials, andenergy utilization of residual waste. This would meanthat the order of priorities in waste treatment is fullyaccepted (reuse, recycling, use of waste for material andenergy purposes).

Croatia is committed to providing separate collec-tions of waste paper, metal, plastics, and glass, wasteelectrical and electronic equipment, waste batteries andaccumulators, end-of-life vehicles, waste tires, waste oil,waste textiles, and medical waste from January 2015. Alocal government should carry out the separate collec-tion of hazardous waste, waste paper, metal, glass, plas-tics, and textiles, and coarse (bulky) waste by way of

● providing one or more functioning recycling yardsor mobile units in its territory;

● setting an appropriate number and types of con-tainers for separate collection of hazardous wasteand waste paper, metal, glass, plastics, and textilesnot covered by the waste management system forspecial category of waste; and

● informing households about the location andchange of location of the recycling yard, mobileunits, and containers for separate collection ofhazardous waste and waste paper, metal, glass,plastics, and textiles, and transport services forbulky waste at the customer’s request.

Furthermore, the first one that stands out in wasteprevention is direct waste prevention in quality and quan-tity terms. It reduces generated waste amounts and itstoxicity either by reducing the quantities within industrialproduction processes or by preventing waste generationthrough changing the lifestyle patterns or applying ade-quate product designs, which are the requirements that,under the Framework Waste Directive, the EU memberstates and their local and regional administration unitsmust transpose into their laws and regulations anddevelop instruments for monitoring their performancein the actual practice. It is expected that the NationalWaste Prevention Programme for the Republic ofCroatia (currently in daft) is going to be one of a docu-ments dedicated to linking elements of the resource effi-ciency and waste policies.

According to the data from the Croatian Agency forEnvironment and Nature (2016), the amount of gener-ated municipal waste in Croatia before 2005 is mainlybased on estimates. From 2006 onward, the amountsare determined on the basis of data reported by thereporting obligation holders, with additionally esti-mated data regarding that part of the population thatis not covered by organized waste collection and themunicipalities for which the data were not reported.The increase of municipal waste amounts was recordedall through 2008, followed by decreasing waste amountsuntil 2010. From 2011 onward, there is a slight increasein waste quantities, which is most probably the result ofadding the municipal waste from the service sector

JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION 245

(packaging waste, paper and cardboard waste, etc.) tothe calculated amounts. In 2013, the increase of totalquantity of produced municipal waste in relation to2011 was 4.6%, and 3% in relation to the previousyear. However, in 2014, there was another reductionin waste quantities, down to the 2010 level, when it wasapproximately 1.6 million tonnes as a result of lowergross domestic product (GDP) and waste productionper capita. Figure 1 shows the values of generatedquantities of municipal waste in Croatia until 2014.

In 2013, the municipal waste generation amountedto 1,720,758 tonnes (402 kg per capita), i.e., dailyamount per capita was 1.1 kg, and in 2014 the amountof generated municipal waste in Croatia was decreasedto 382 kg per capita, which is below the EU average.The available Eurostat data on average annual house-hold waste generation per capita show that in 2013 eachperson in the EU generated 477 kg of municipal waste.Recent data for 2014 processed at the level of the EUshow decreasing trend of municipal waste generationper capita. Thus, at EU28 level 475 kg of waste wasgenerated (a decline of 0.5% compared with 2013)(Eurostat, 2016).

In Croatia in 2013, 76% of total collected waste or1,299,577 tonnes was mixed municipal waste, and in2014 it made 79%, or 1,308,122 tonnes. The amount ofother types of municipal waste that were directed torecovery in 2013 was 258,056 tonnes, and in 2014 thisamount was 172,421 tonnes (CAEN, 2016).

The first obligation of the Republic of Croatiaregarding the reduction of municipal waste landfillingrefers to the biodegradable waste component. Namely,the goal concerning landfilling in Croatia is regulatedby the Act on Sustainable Waste Management, whichlays down the amounts of maximum allowable biode-gradable municipal waste that can be depositedannually in all landfills and noncomplaint landfills inthe Republic of Croatia, in relation to the 1997 level ofmass of biodegradable municipal waste generation.These amounts are:

● 75% or 567,131 tonnes by 31 December 2013;● 50% or 378,088 tonnes by 31 December 2016; and● 35% or 264,661 tonnes by 31 December 2020.

The trends in landfilling of biodegradable municipalwaste over years in relation to the prescribed goals inthe Republic of Croatia are presented in Figure 2.

The targets have been put in place in regard todiverting biodegradable waste from landfill, and inorder to meet them, countries’ waste managementstrategies and policies are being changed and devel-oped. The comparisons between the strategies, ateither country or region levels, proved to be a usefulmethod of assessing the effectiveness and drawbacksof the various strategies (Morrissey and Phillips, 2007;Mühle et al., 2010).

The first target in reducing landfilling of biodegrad-able municipal waste with 31 December 2013 deadline,of 567,131 tonnes, had not been achieved because thetotal reported quantity of landfilled biodegradablemunicipal waste in 2013 was 870,434 tonnes. The quan-tities of waste of all types deposited in all landfills in theRepublic of Croatia at end of 2013 exceeded theplanned and allowed levels by 20.1%, so that the quan-tity of biodegradable waste was 53.5% above the allow-able maximum (out of which 17% comes from the cityof Zagreb). A similar scenario can also be foreseen for2016, because on the basis of the 2013, 2016, and 2020targets, it is possible to determine the targets for reduc-tion of landfilling of biodegradable municipal wastemass by end of 2020 (Figure 3), which are significantlylower than the values of actual landfilling.

Considering the experience so far as well as the targetsfor biodegradable municipal waste landfilling, the intro-duction of and improvements in separate collection ofbiodegradable municipal waste in the city of Zagrebmust be set as a priority. Otherwise, the goals and targetsat the national level will certainly remain beyond reacheven after 2020, the year set as a final deadline.

Figure 1. Quantities of landfilled municipal waste over years in the Republic of Croatia (CAEN, 2016).

246 B. RIBIĆ ET AL.

Particular emphasis has been placed on the diversionof biodegradable municipal waste for a number ofreasons. When landfilled, the anaerobic degradation ofthe putrescible fraction of biodegradable waste causesthe release of greenhouse gases (GHG), especiallymethane, if not properly managed. Dealing with biode-gradable municipal waste effectively can bring about anoverall reduction in a country’s GHG emissions, aidingcompliance with GHG emission reduction targets setunder the Kyoto Protocol (Zavodska et al., 2014).

Demographic indicator

As the capital of Croatia, the city of Zagreb is a localself-government unit with a status of regional self-administration. Its area stretches over 641.32 km2, andit consists of 17 districts. According to the 2011 census,Zagreb has a population of around 790,000 (CroatianBureau of Statistics, 2014). The organized municipal

waste collection in the city covers around 360,000 ser-vice users (data for 2012), out of which 350,000 areresidential users (two thirds of the users live in resi-dential buildings and one third in family houses). Thereare about 10,000 commercial users. In the city, themixed municipal waste from households is collectedmainly in containers and bins, and only a small portionin plastic bags.

Waste generation in the city of Zagreb

The landfill site of the city of Zagreb was established in1965 as an “illegal” city landfill on an undevelopedpiece of land on shallow gravel pits and backwatersnear the Sava River right bank. In this way, an impro-vised landfill was formed on an area of more than 80hectares in the immediate vicinity of city’s residentialareas, at about 5 km distance from its very center. Thefirst investigations were carried out between 1986 and

Figure 2. Landfilling biodegradable municipal waste over years in relation to the prescribed targets in the Republic of Croatia (CAEN, 2016).

Figure 3. Targets for gradual reduction of biodegradable municipal waste mass allowed to be deposited in the landfills in theRepublic of Croatia (CAEN, 2016).

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1988, which confirmed the influence of the depositedwaste on the quality of underground water. This isbecause of all way through the mid-1990s, the munici-pal, technological, and probably hazardous wastes hadbeen deposited without any control. It is estimated thatso far the Zagreb landfill has received more than 12million tonnes of waste.

In early 1990s, the city administration initiated thework on a conceptual plan of clearing up and shuttingdown this landfill. The plan was put in motion in 1995by recovery of the first surface. The recovery was car-ried out in the way that the on those places that werecleared from the old waste, the new surfaces withimpermeable sealing system and peripheral ridge weredeveloped. On these new surfaces, the old but also thenew wastes were placed. Because of this, all the waythrough 2004 the new waste was deposited togetherwith removing the old waste at the same time. Themobile thermal unit for treating hazardous waste wasbuilt in 1997, with capacity of 10 thousand tonnes. Itwas closed down in 2002 after a fire had broken out inthe unit’s temporary storage unit.

Although the Physical Plan of the City of Zagrebenvisaged the recovery of the landfill by 2005, and thedepositing waste on the remediated surfaces shouldhave been ended by 2010 at the latest, the deadlinefor decommissioning the landfill and opening of theWaste Management Centre, any of this has not hap-pened yet. The Decision Amending the Physical Plan ofthe City of Zagreb states that the capacity and technicalfacilities of the landfill site ensure the conditions forlandfilling waste on the newly developed surfaces until31 December 2018 and that neither the thermal treat-ment unit nor Waste Management Centre has beenconstructed. Presently, depositing waste on the landfillis the only waste management measure in the city.After closing down the landfill, the plan is to remediatethe surface into a reclaimed green area with recrea-tional facilities, without permanent residential build-ings. Currently, it is possible to carry out sorting andpretreatment of municipal waste, bulk waste, and con-struction waste, to sort separately collected waste frac-tions, and carry out biological treatment of waste in theexisting composting unit.

Furthermore, for comparing only capitals cities in theEU, waste generation in 28 EU capital cities ranges fromaround 270 kg per capita (Dublin) up to 666 kg percapita (Luxembourg), with the average at 445 kg percapita of municipal waste. Zagreb’s value (386 kg percapita) is 13% lower than the average EU value. Thesedifferences can be partially explained by econometricfactors (such as household size, household expenditure,or gross domestic product [GDP]) and other factors

such as number of visiting tourists and daily commuters.However, one key explanation is that each member stateincludes different types/sources of waste in the statisticaldata on waste generation (EU Directorate-General forEnvironment [EU-DG Environment], 2015). Regardingthe waste management in the EU, it is more than obviousthat significant efforts have been made in the recentdecade toward the diversion from landfill. Specialemphasis has been given to the improvement of thebiowaste management in various EU municipalitieswhere waste management companies are introducingseparate collection with clear economic and environ-mental benefits (Ribić et al., 2015).

According to the data from CAEN (2016), Zagreb’sannual waste disposal amounts to approximately450,000 tonnes of all types of waste, out of which muni-cipal waste makes up 437,000 tonnes. Figure 4 showstotal quantities of mixed municipal waste, which, before2014, was deposited at the city’s landfill site.

Figure 4 makes it evident that the quantities areabove all the targets, which in the near future will behard to achieve; it also shows that from 2012 to 2014there was hardly any progress in this direction at thecity level in terms of volume of mixed municipal waste,which was deposited in the landfill. Because of theobligation to close down the landfill site by end of2018, it is necessary to find a quick and efficient solu-tion for waste management in the city of Zagreb thatwill be based on circular economy of waste manage-ment and minimum possible wasting of resourcesthrough landfilling waste without being pretreated.The importance of introducing the circular economyprinciple in the Zagreb City region becomes evident inthe light of the fact that Zagreb generates as much as21% of total waste in Croatia. Due to this reason, thereform of the present city’s waste management systemis crucial in order to introduce a more efficient separatewaste collection as well as the use of other technologiesof mixed municipal waste recovery, all with the aim tomeet the obligations regarding the waste management.

The important starting points for developing anyproposal for an efficient waste management systemare analysis and assessment of the present practices inwaste management and waste prevention in the city ofZagreb, using the available data about waste and wasteprevention measures and activities. Also, the analysis ofthe current legislative and regulatory framework at thenational, regional, and local levels is essential for deter-mining the required amendments as well as for identi-fication of those thematic areas that still have notaddressed the waste prevention issues. All future pro-posals for addressing waste management, in theRepublic of Croatia and the city of Zagreb, depend on

248 B. RIBIĆ ET AL.

the composition of the municipal waste itself. Theaverage composition of the municipal waste in thecity of Zagreb is given in Figure 5, which shows thatthe largest portion is biodegradable waste (about 63%).

Tightening the European Union legislation requiresa reduction in the quantity of municipal waste sent tolandfill, with a particular emphasis on biodegradablemunicipal waste (EEA, 2015). Biodegradable municipalwaste comprises the parts of household, commercial,and cleansing wastes that will biologically degrade, andis typically composed of food and garden wastes, wood,paper, cardboard, and textiles. Figure 6 shows thevalues of biodegradable waste deposited at the landfillsite of the city of Zagreb.

Namely, in accordance with the obligations relatedto biodegradable waste that the Republic of Croatia hasundertaken, by end of 2016 the maximum of 64,274tonnes of biodegradable municipal waste can be land-filled in the Zagreb region. This means that by end of

2016, the allowed mass of biodegradable waste depos-ited on the landfill must be reduced from the 2012 levelby 81,668 tonnes, or 56% of total landfilled biodegrad-able waste. For the year 2020, the allowed landfilling ofbiodegradable waste is even lower and amounts to only44,992 tonnes, which is a reduction by 100,950 tonnesor as much as 69% of total biodegradable waste in 2012.Since in 2012 the amount of biodegradable waste land-filled at the Zagreb’s landfill site was as high as 145,942tonnes, it is evident that these obligations will not befulfilled and that the separate biodegradable waste col-lection system is quite underperforming. To put thedata into perspective, it results that out of the totalwaste amounts in Croatia, as much as almost 17% ofbiodegradable waste is landfilled in Zagreb. It can beconcluded that without introducing an efficient systemfor separate collection of biodegradable waste at the cityof Zagreb level, it will be very hard to achieve thetargets at the national level.

Figure 4. Mass of landfilled mixed municipal waste of the city of Zagreb in relation to obligations and quantities allowed to belandfilled (CAEN, 2016).

Figure 5. Municipal waste composition in the city of Zagreb (IPZ Uniprojekt Terra, 2010).

JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION 249

As for the separate waste collection in the city ofZagreb, paper and cardboard, glass, and waste plasticsare collected in the bins and containers placed in thepublic areas. In addition, paper and cardboard arecollected in bundles by special vehicles that tour inthe afternoon and evening hours the locations wheresuch waste is generated on a daily basis (shops, com-mercial centers, etc.).

Waste paper and cardboard are collected through asystem of 2029 blue containers, of 2 and 3 m3 involume, which are placed on public surfaces, and inrecycling yards and green islands. There is also a systemfor collecting waste glass packaging, consisting of 1547green containers placed on public surfaces. Reusableglass packaging is mainly collected in the shops thatare regulated by special regulations.

The system of 1488 yellow containers of 1.1 and 0.7 m3

in volume installed on public surfaces in the city of Zagrebis in place for collection of nonrefundable waste plasticpackaging and other, reusable, plastics. Given the fact thatplastic packaging is covered by the special Ordinance onPackaging and Packaging Waste (Official Gazette, 2005,2015 [97/05; 88/15]), the largest portion of this type ofwaste (drinks and beverages packaging) is collected in theshops in accordance with the special regulations. Until2006, the plastic waste was collected only through a sys-tem of the yellow containers placed on public surfaces;with the coming into force of theOrdinance on Packagingand Packaging Waste and classification of plastic materi-als into refundable drinks and beverages packaging andother plastics, the amount of plastic waste collected in theyellow containers and bins dropped significantly.

Only in 2015, 91 containers for separate collectionof textiles and footwear were placed. Also, there arenine recycling yards where citizens can dispose of allseparate waste without charge (more than 20 types ofwaste).

Table 1 shows total annual amounts of waste paperand cardboard, glass, plastics, metal, and textiles thatare collected from the municipal waste disposed of inthe public containers and recycling yards.

Based on the data in Table 1, it is possible tocalculate the annual quantities of separately collectedwaste in the system operated in the city of Zagrebthrough its utility company. The results are the fol-lowing: 1.91 kg of paper and cardboard; 1.62 kg ofglass; 0.52 kg of plastics; 0.02 kg of metal; and 0.19 kgof textiles are collected per inhabitant annually.Overall, it amounts to approximately 4.26 kg of sepa-rately collected waste per year, or a modest 1.1% oftotal generated waste per inhabitant of the city ofZagreb. If other methods of waste collecting, operatedoutside the city-owned utility company system, areadded to this picture, with an overall total of slightlybelow 5 kg per capita, the city of Zagreb has thelowest ranking among the EU28 capitals. For refer-ence, the highest collection rate is 189 kg per capita(Luxembourg) including all five fractions, andLjubljana, Rome, Stockholm, Tallinn, and Vienna per-form very well in terms of quantities collected, withannual amounts exceeding 160 kg per capita. Onaverage, the EU capitals separately collect 80 kg percapita of paper/cardboard, plastics, glass, and biowaste,and an average of 108 kg per capita once other frac-tions are included (e.g., bulky waste). This means that,on average, only 19% of generated municipal waste iscollected separately in the EU28 capitals: in otherwords, 80% of the waste still ends up in the residualwaste bins (EU-DG Environment, 2015). Therefore,although the Zagreb City infrastructure has beendeveloped, the waste collection within the systemsoperated by the city’s utility company does not givethe results that would contribute to fulfillment of therequirements imposed by the EU.

Figure 6. Mass of landfilled biodegradable waste in the city of Zagreb in relation to obligations and quantities allowed to belandfilled.

250 B. RIBIĆ ET AL.

Although comparing the countries’ waste statisticscan be a useful exercise in quantifying possibleimprovements, this comparison of Eurostat data hashighlighted the difficulties in achieving meaningfulcomparisons due to differences in reporting and defini-tions. Of the 481 kg of municipal waste generated percapita in the EU in 2013, 470 kg were treated. Thistreatment followed different methods: 31% was land-filled, 28% recycled, 26% incinerated, and 15% com-posted. The share of municipal waste recycled orcomposted in the EU has steadily increased over thetime period, from 18% in 1995 to 43% in 2013. Basedon the reports from waste collecting operators, about10% of municipal waste was sent directly to recovery.However, if we take into account the quantities ofmunicipal waste from the service sector, the estimateis that around 20% of waste collected by city-basedoperators is recycled. Accordingly, the present wastemanagement system, as organized by the city ofZagreb, is inefficient and inadequate, and further activ-ities must be focused on creating conditions for sepa-rate waste collection and recovery.

The regular collection and transport of bulky wastefrom the Zagreb households is organized twice a yearon an on-demand basis. The green market waste iscollected daily from 23 locations. The collected muni-cipal waste from green markets, excluding biowaste anduseful waste, is transported to the city’s landfill site.

Cleaning and washing the public surfaces is one ofthe municipal activities performed in the city. Thecleaning is carried out for sanitation, security, andesthetical reasons. This is a way to prevent variouswaste materials such as dirt and stones, road salt,glass or metal or plastic debris, papers, leaves, etc.,getting into the municipal sewerage system or surfacewaters. These waste materials are, under the specialregulation, defined as residues from street cleaning,and within the current system, this waste is disposedof in the city’s landfill.

According to the law, production waste is defined asthe waste generated during production process inindustrial, craft, and other processes, and its composi-tion and properties make it different from municipalwaste. The production waste in Zagreb City is collectedby a number of licensed operators, legal persons whohave obtained an appropriate waste managementlicense. Construction waste produced in the past severalyears in the city’s regions can be classified mainly underseveral key types of waste, namely, concrete, brick, rooftiles, ceramics, mixed construction waste, and postde-molition waste. At the landfill site, a unit for recyclingconstruction waste has been built and processes thiswaste into recycled material used for covering wasteand building access roads to the site itself. Table 2shows the quantities of bulky and production wasteslandfilled at the Zagreb’s landfill site, waste from greenmarkets, street cleaning waste, and construction waste.

Biowaste, as a fraction with the highest share in totalbiodegradable municipal waste, represents one of thegreatest challenges in establishing a sustainable wastemanagement system. The separate collection of biowasteat location of its generation generally results in betterquality of the substrate due to lower content of impurities(such as plastic residues, metal compounds, glass packa-ging, etc.) when compared with mechanically separatedorganic waste from mass of municipal waste. Municipalwaste mostly consists of organic waste, including kitchen

Table 1. Total quantities of separate collected waste through containers and recycling yards organized by the city of Zagreb UtilityCompany (waste paper and cardboard, glass, plastics, and textiles).

Year

Paper and cardboard Glass Plastics Metal Textiles

Containers(t)

Recyclingyards (t)

Containers(t)

Recyclingyards (t)

Containers(t)

Recyclingyards (t)

Containers(t)

Recyclingyards (t)

Containers(t)

Recyclingyards (t)

2007 3471 538 107 23 0 26 0 0 0 02008 2679 892 13 3 9 16 0 670 0 02009 2927 538 237 64 24 237 0 437 0 02010 2546 479 841 51 50 274 0 398 0 02011 897 151 760 28 79 91 0 0 0 02012 1567 188 775 32 177 25 0 0 0 02013 2953 330 909 42 336 360 3 0 0 02014 1443 436 1054 50 487 0.6 3 4 0 0.142015 1141 329 1182 60 379 20 4 13 66 82

Table 2. Quantities of production waste landfilled in the city ofZagreb landfill sites.

Year

Landfilledbulky

waste (t)Productionwaste (t)

Landfilledgreenmarketwaste (t)

Landfilledstreet

cleaningwaste (t)

Landfilledconstructionwaste (t)

2007 57,817 16,431 3019 8874 15,7972008 62,439 9113 3170 9097 12,8532009 49,878 5097 3662 5719 65842010 91,171 6397 3916 5575 13,4132011 50,412 9757 3021 4125 13,0502012 24,711 7504 3102 3715 11,122

JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION 251

waste, food residues, waste from food industry, grass,wood, paper and cardboard, etc. “Green waste,” as a partof municipal waste, mainly consists of garden waste andwaste generated in the public parks. The collected bio-waste is generally transported to composting units. Totalannual quantities of treated biowaste are given in Figure 7.

The Act on Sustainable Waste Management definesthe limits for landfilling of biodegradable waste and thelimits for disposing of waste in noncompliant landfills.Before 2016, the amounts of biodegradable and land-filled wastes in the city of Zagreb were between 70,000and 80,000 tonnes.

A particularly interesting type of biodegradablewaste is fats and oils. The method of dealing with edibleoils waste is regulated by a special ordinance that dealswith waste oil management (Official Gazette, 2006[124/06]). Edible fats and oils are a raw material forbiodiesel production and, as such, are highly market-able. Based on the data from CAEN (2016), during2010 the amount of collected waste edible oils andfats in the city of Zagreb was 34.8 tonnes. It is consid-ered that the quantity of waste edible oils is muchbigger, and this waste is generally exported into neigh-boring countries as a raw material for biodiesel.

Irregular landfills in the Zagreb City region are beingcleared up by orders of the Municipal Monitoring Officeand environmental inspections. In the process of wastecollection, metal waste, waste electrical and electronicequipment, waste tires, and possibly some other poten-tially hazardous material, if present, are collected sepa-rately on the spot. These types of waste are then handedover to the licensed companies for further processing, asrequired. The remaining waste, which by its composition,is similar to bulky waste is transported to the Zagreblandfill. Figure 8 shows total annual quantities of wastefrom irregular landfills of the city of Zagreb.

Proposed concept of sustainable wastemanagement in the city of Zagreb

This paper has made evident so far that the currentwaste management system in the city of Zagrebneeds to be essentially improved in order to makeit more resource efficient, as well as to shift thecurrent practice upward in the waste managementhierarchy (i.e., to reduce significantly waste disposal,and focus on waste prevention, reuse, recycling, andrecovery). One of the main reasons why currentwaste management system is not sustainable is lowrecycling rate, especially for waste produced in thehouseholds. According to the latest study performedby the EC, the city of Zagreb has one of the poorestperforming waste management systems of all capi-tals in the EU (BiPRO/Copenhagen ResourceInstitute [CRI], 2015). The same study has showngood practice examples in different EU capital cities,with the conclusion that source separation is themost effective way and that it is necessary to havelarge citizen engagement in all processes related towaste management.

In historical perspective, Croatia, including thecity of Zagreb, has been very dependent on landfill-ing as a means of municipal solid waste disposal,mainly for the same reasons as other EasternEurope countries: low or no landfill fees and a lackof other options. In many cases, it is still the cheapestwaste management option in Croatia. However, by2018, the city’s landfill is planned for closing downand the city of Zagreb needs to introduce a newmethod of waste management. The new systemmust aim at establishing a sustainable waste manage-ment and meeting the targets set up by the EUdirectives (EC, 2008) and by the applicable law. Itshould be based on the following activities:

Figure 7. Total annual quantities of treated biowaste in composting units of the city of Zagreb.

252 B. RIBIĆ ET AL.

● Waste prevention and reduction of the amounts oftotal waste generation, and establishing of systemof product reuse

● Improvement of the present separate collectionsystem by increasing the number of the “greenislands” and recycling yards and their efficiency

● Introduction of separate collection of biowaste fromlarge producers, and construction of anaerobicdecomposition units for bio-methane production

● Construction of a sorting unit for separately col-lected waste fractions

● Construction of automated separation plant for thewaste left out of the system of separate collection

The proposal for the system with main waste flows isdescribed in Figure 9. This figure also represents theproposed solution for sustainable waste management inthe city of Zagreb, where the emphasis has been givento the separate waste collection and recycling of differ-ent waste streams, such as paper, plastic, glass, metal,and textile, and biowaste. Recycled materials would besent for material recovery, and biowaste would be usedfor energy utilization. Residual municipal waste, whoseamount after source separation is significantlydecreased, would be sent to mechanical separationwith the priority to separate useful waste for recycling.After all these processes, small quantities unused waste

Figure 8. Total annual waste quantities from irregular landfills.

Figure 9. Proposal for waste management system in the city of Zagreb.

JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION 253

would be used either for energy recovery or sent tolandfill.

Given the fact that the waste management is closelyconnected to the EU legislative framework, waste pre-vention should be one of the priorities, and it must beseen as a multidisciplinary field. Waste prevention interms of reduction of waste amounts is not related onlyto environmental protection policies but also cutsacross several specific areas, which are not directlyconcerned with these issues (innovation policy, educa-tion policies, etc.) (Carvalho and Marques, 2014).During the implementation of several pilot projects inthe Zagreb City region that deal with useful wasteseparation, it was noticed that the waste producers(citizens) have become increasingly aware of the needto prevent and reduce waste as well as of the need forbetter implementation of the environmental protectionin general. The establishing of a waste reuse systemaims at reduction of landfilling, extending of product’slife cycle, and protection of standard of living, creationof new jobs, and utilization of local resources.

The existing waste management system as a wholeshould be redefined in accordance with the proposalpresented in Figure 9. Within this context, there is anurgent need to increase the quantities of separatelycollected waste. It is also essential to optimize thenumber of the bins for separate waste fractions(paper/cardboard, plastic/metal, glass, and textile) andtheir placement in the locations all over the city.Further, since the current system of monitoring thequantities of separately collected waste is not efficientenough, it is necessary to implement informatizationand to introduce optimal waste transport programs.The separate collection system should be upgraded byincreasing the number of “green islands“ so that onebin or container for each waste fraction would coverthe needs of 180–200 households, giving a priority toprimary recycling by degree of material recovery of thecollected waste fractions. The pilot projects of separatecollection carried out in Zagreb showed, among otherthings, that the public is aware of the advantages ofwaste separation, with strong will to participate. Inorder to have their complete involvement, besides theeducational, also day-to-day activities should be orga-nized. This will certainly increase the amounts and thequality of separately collected waste fractions, which isunfortunately at the moment not satisfactory, and thequantities are still rather low. During the implementa-tion of the pilot project, different workshops and pre-sentations were introduced to the citizens, with veryvaluable outcome.

Especially problematic is the polymeric waste, whichdue to high impurity contents has a rather low

recycling rate. Due to this, it is necessary to build asorting unit for waste fractions collected in the Zagrebregion, where different polymer fractions (polyethyleneterephthalate [PET], high-density polyethylene[HDPE], low-density polyethylene [LDPE], polypropy-lene [PP], etc.) would be separated. Such a unit wouldbe fully automated and equipped with optical sensors,thus reducing to a minimum the need for manual work.Separately collected paper should also be sorted (card-board packaging, newspapers, etc.) because it helps toachieve a significant economic benefit by selling themixed paper for reuse.

Separately collecting specific fractions from munici-pal waste requires not only the implementation of anadequate collection system but also the active participa-tion of the citizens. Individuals must understand theirrole in the waste management scenario and cooperatewith the local authorities for the system to work.Adding to that, the public must be confident that anymaterial they source-separated for recycling is sent forrecycling and not landfilled or incinerated (Bortoletoet al., 2007).

The level of citizens’ engagement has a direct impacton the efficiency of a collection system. Where systemchanges are necessary, effective communication isneeded to inform the public of its benefits. Properlyinforming citizens about the type and kind of wastethat should be placed in separate bins is vital for redu-cing impurities and obtaining a high-quality recyclablematerial. On the other hand, public participation playsa vital role in providing critical information to lawenforcement agencies. A great deal can be done byeducating people and impressing upon them the con-sequences of illegal dumping and improper waste man-agement that may create life-threatening conditions(Hasan, 2004).

It is crucial for Zagreb to improve the rate of sepa-rately collected waste and move away from the rear endof the EU28 capitals ranking list, as one of the rarecities that has not an efficient system of sustainablewaste management. It is possible to start introducingsuch improvements in useful waste management sys-tem (primary recycling) in 2016 already, but any sig-nificant progress (increasing quantities of separatewaste) cannot be expected before 2017.

Because of the fact that a system of separate wastecollection must be introduced quickly (due to legalrequirements and EU obligations), it is necessary tostart with separate collection of organic biodegradableportion (i.e., biowaste as a specific fraction) of munici-pal waste as soon as feasible. Of the five separatelycollected fractions, biowaste has the highest generationlevel within municipal solid waste. Nevertheless, its

254 B. RIBIĆ ET AL.

diversion from landfill will have significant positiveimpact to the environment (Bjorklund et al., 1999).

Therefore, the separate collection of biowaste is aprime candidate for significantly increasing total sepa-rately collected amounts. This is supported by the rela-tively high yields of collected biowaste, especiallyconsidering that waste collection does not share thelong recycling history of more (commercially) valuablematerials such as paper and glass. The system of bio-waste collection in Zagreb should be focused firstlytowards large biowaste producers, such as food industrywith agricultural products processing, i.e., food andbeverage industry, green markets and commercial cen-ters, service sector centers, and agricultural producers.After that, such system of biowaste separate collectionshould also involve family houses, which besideskitchen waste produce large amounts of green waste(branches, grass, leaves, etc.).

In residential buildings, it is the kitchen waste that ismainly collected (food scraps, fruits, vegetables, etc.),and that biowaste is partly liquid, which makes it man-datory to collect it in biodegradable bags. Therefore,collecting bins should be placed in city neighborhoodsfor this purpose. The collection of biowaste is logisticallyorganized by use of special separating containers thatwould be distributed to the households, or would beplaced in special spaces in multistory buildings. Thecontainers for biowaste disposal have volume of 120and 240 L and, if required, possibly 1100 L. The contain-ers for collecting separate biowaste should be distributedto the households, schools, kindergartens, institutions,small businesses, hotels, and restaurants. The biowastegenerated at commercial centers and large producerswould be collected in large bins and containers.

Energy use of biowaste collected in this way wouldbe performed through anaerobic digestion and biogasproduction. Such biowaste treatment has two positiveeffects: landfilling prevention and production of animportant energy source with potentially multipleusage. Main advantage of anaerobic digestion com-pared with the composting is energy productionthrough the optimal utilization of biogas from bio-waste, which, upgraded to natural gas (methane) qual-ity, would be in city public transport, where it would beused as fuel for pressurized natural gas–powered buses.So far, within the city of Zagreb, there are 100 com-pressed natural gas (CNG) busses that are operating inthe public transport, and two CNG filling stations.

Also, it would be possible to directly connectupgraded biogas to the city gas network. Likewise,there is an option of using biogas in cogenerationunits, producing electricity and heat, but it presumesthe consumption of heat throughout the year. The fact

that in the city of Zagreb, every year 30% of generatedbiowaste comes from the municipal waste (Figure 5) isan argument in favor of such utilization of biowaste,because this quantity would be sufficient for running abiogas plant of 2 MWel of rated capacity. The fermen-ted residue, or biowaste from anaerobic digestion, doesnot have odor nuisance; thus, its disposal does notcause this kind of problem for the population in thevicinity of the disposal site. It can also be used ascompost for the city’s public green surfaces.

The described activities in biowaste management canbe launched in 2016 (for example, enlarging the area fromwhich green waste is taken away), because such waste canbe disposed of at the site where a composting unit islocated. If the construction of biogas plant starts in 2016(drafting project documentation), the plant could beoperational by 2019, enabling the city to significantlyincrease the amounts of separately collected biowaste(especially biowaste from households and services).

By implementing all these activities, the city ofZagreb will certainly make a big step towards introdu-cing a sustainable waste management system andimproving useful waste separation. Given the fact thatthe present recycling rate of the main fractions (paper,plastic, biowaste) is rather low and the targets appear tobe hardly achievable within the given deadline andwithin the primary recycling system, the fundamentalproblem to be addressed in the future is how to treatthe mixed waste that will continue to be generated inthe Zagreb region. Due to this, it is necessary to build aplant for automated separation of mixed municipalwaste where useful fractions would be separated (e.g.,paper, plastic, glass, metal, biowaste), thus in this wayimproving the system of primary recycling.

Namely, it is necessary to separate any waste that isnot covered by the separate collection system, firstlyinto biodegradable fraction, and all other useful frac-tions after that (paper, metal, glass, plastic), and onlythen to separate the fraction used for preparation ofrefuse-derived fuel (RDF), which would be a fuel forenergy recovery (as replacement fuel for cement indus-try fuel, for example). The biodegradable fraction fromthe plant would be used for energy recovery in theprocess of anaerobic digestion, in the same way asother separately collected biowaste, and since theobtained fermented residue has a satisfactory organiccarbon content, its landfilling is allowed. This methodof treating mixed municipal waste and separation ofuseful components and their reuse is equivalent to theseparate waste collection at place of generation andrecovery. The preparation for developing the auto-mated mechanical separation unit should start in2016, so that it could be operational by end of 2019.

JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION 255

Unfortunately, the time frame for all of these activ-ities is still unclear due to the current lack of wastemanagement plan for the city of Zagreb.

Table 3 shows the current situation of differentwaste streams produced as a part of mixed municipalwaste in 2012, in accordance with the composition ofmixed municipal waste system in Zagreb presented inFigure 5. In the table are also presented figures regard-ing the reduction of municipal waste quantities byfractions by 31 December 2020. Based on the approachthat all targets will not be achieved only by sourceseparation, amounts of mechanical separation are alsoprovided in the table. The measures for waste preven-tion and recovery are included in the activities relatedto separate collection and sorting.

The first target of annual 65% cutting down onlandfilling of biodegradable municipal waste by 31December 2020 from the 2012 level of 94,577 tonneswill be a challenge if midterm targets have not beenachieved. The midterm targets should be met at the endof each calendar year. Also, it is necessary to organizeseparate collection of other waste fractions, i.e., it ispossible to envisage a scenario based on the targetsfor December 2020. Based on this and in accordancewith the introduction of the new system of separatecollection, it is possible to determine the targets forstep-by-step increase of separate collection of variousfractions of mixed municipal waste by end of 2020(Figure 10), on the basis of the targets set by the EUwaste and landfill directives.

As all the data mentioned in the paper show, the rate ofmunicipal waste recycling in the city of Zagreb is still verylow andmuch lower than in other capital cities of the EU.On the other hand, the data in Table 3 and Figures 9 and10 demonstrate that a relatively high municipal wasterecycling rate can be achieved by introducing the newwaste management system in the city of Zagreb.

There is a distinct impression that once the wastemanagement and recycling system starts operating inthe city of Zagreb, a lot of work is needed on educationof the citizens, in order to have them become familiarwith the system and to encourage their participation infinding solutions for a waste management that willwork for the benefit of all city’s inhabitants.

As we look into the future, it is important to keep inmind that municipal waste management in the city ofZagreb cannot be addressed simply as a technical, environ-mental, economic, or social issue, because all these aspectsare closely interconnected. Improving waste managementpractices and making them as efficient as possible is goingto be one of the most important environmental challengesCroatia will face in the future.

In light of all mentioned above, it is more than obviousthat city of Zagreb needs in the future time to significantlyinvest in order to set up an efficient waste managementsystem that will be not only ecologically but also econom-ically sustainable. Main investments should be in settingup more efficient source-separation scheme (increase thenumber of recycling yards and “green islands”), biogasplant, and mechanical separation facility.

Based on the information gathered in similar EUcities (city of Hannover, city of Ljubljana), approximateinitial investment costs are around €55 million.

Conclusion

It is considered that sustainable waste management has ahuge potential of development not only for the city ofZagreb but for Croatia as well. There is strong need tointroduce integral solid waste management system basedon circular economy principles, whichwould strictly followthe waste management hierarchy. Given the fact that thepresent rate of recycling useful components of waste in thecity of Zagreb is significantly below the targets set out by

Table 3. Overview of trends in municipal waste quantities in the city of Zagreb until 31 December 2020 in the proposed model ofmunicipal waste management.

Assumed quantities after implementation of the proposai (t)

Type of waste Quantity in 2012 (t)Required reduction of quantities

by 31 December 2020 (t)Separate waste collection

and sorting (t)Automatic mechanical

separation (t)

Mixed municipal waste 233,928 138.789,4

Paper and cardboard 63,628.4 41,358.5 17,784.1 23,574.3Kitchen biowaste 61,990.9 40,294.1 17,729.1 22,564.7Garden biowaste 9591.0 6234.2 4363.9 1870.3Wood 2339.3 1520.5 988.3 532.2Textile 7953.6 5169.8 3877.4 1292.5

Glass 8421.4 4210.7 2737.0 1473.7Plastic 61,523.1 30,761.5 16,303.6 14,457.9Metal 2573.2 1286.6 386.0 900.6Diapers 12,866.0 6433 0 6433.0Inert waste 1637.5 818.7 0 818.7Miscellaneous 1403.6 701.8 0 701.8

Total 233.928 130,845.4 64,169.7 74,619.7

256 B. RIBIĆ ET AL.

the EU, it is necessary to start to improve the currentprimary recycling system with a view to increasing therate of waste separation. The upgrade of the existing systemof waste management would result in considerable reduc-tion of landfilling of all types of waste and fulfilling EUtargets in waste and landfilling directives. The proposedwaste management model should result in avoidance ofwaste generation and a reduction of waste amounts atsource and to be disposed of, with a simultaneous increasein material and energy recovery. Reducing waste can resultin many environmental, economic, and social benefits. It isimportant to keep on mind that sustainable waste manage-ment model in the city of Zagreb cannot be treated simplyas a technical, environmental, or economic project becausewaste management requires a collaborative approach, withstrategic partnerships between government, local authori-ties, experts, and general public.

Waste can be prevented only by involving the publicbecause people should be encouraged to separate morequantities of municipal solid waste for recycling or com-posting. For that reason, it is necessary to organize perma-nent and comprehensive education of the public andgovernmental institutions about the benefits of abandoninglandfilling as a current situation and solution for waste inthe region of the city of Zagreb.

Funding

The authors would like to acknowledge the Bin2Grid projectfor its financial support. This project has received funding

from the European Union’s Horizon 2020 research and inno-vation program under grant agreement number 646560. Anycommunication activity related to the action must indicatethat it reflects only the author’s view and that theCommission is not responsible for any use that may bemade of the information it contains.

About the authors

Bojan Ribić, Ph.D. student, is a head of the Department forProjects and Cooperation in City Waste Disposal, Zagreb(Croatia) City Holding, and coordinator of Horizon 2020project Bin2Grid.

Neven Voća, Ph.D., is an associate professor at the Faculty ofAgriculture, University of Zagreb, Zagreb, Croatia.

Branka Ilakovac, Ph.D. student, is the head of the publicrelations department in the Croatian Agency forEnvironment and Nature.

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Figure 10. Midterm targets regarding separate collection of mixed municipal waste fractions by proposed model for separate wastecollection.

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